1. Field of the Invention
The present disclosure relates to a switchgear having a disconnecting switch and an earthing switch, and more particularly, to a three-position actuator for a switchgear capable of overcoming the problems of a three-position actuator for a switchgear using a single drive shaft which involves the risk of electric shortage due to an overrun.
2. Description of the Conventional Art
A switchgear having a disconnecting switch and an earthing switch is electrical power receiving and transforming equipment which is capable of opening or closing electric lines (the electric power circuit) in the operation and maintenance/repair of an electric power system.
Examples of the switchgear include a gas insulated switchgear with an insulating gas as an interphase insulating medium filled in a case and a solid insulated switchgear using a solid insulating material, such as epoxy, as an insulating medium. For opening, closing and earthing operations of the disconnecting switch in the switchgear, a three-position actuator is used to actuate to three positions including a circuit closing position, an circuit opening position, and an earthing position.
Conventional Example 1 of the three-position switchgear for a switchgear was disclosed in Korean Patent Registration No. 10-0146092 (titled “Gas-Insulated Load Switch and Earthing Method Using the Same”) filed by the applicant of the present invention. Conventional Example 2 of the three-position actuator for a switchgear was disclosed in Korean Patent Registration No. 10-0566435 (titled “Three-Position Load Switch With Instant Trip Mechanism”) filed by the applicant of the present invention.
Conventional Example 1 concerns an actuator capable of actuating three positions including a circuit closing position, an circuit opening position, and an earthing position by a single drive shaft, which involves the risk of electric shortage or ground fault when the rotation of one drive shaft overruns more than an angle required to actuate to the respective positions.
The actuator disclosed in Conventional Example 2 is a three-position actuator according to Conventional Example 1 to which an instant trip mechanism is added. Like Conventional Example 1, a single drive shaft is provided for three-position actuation, and therefore the rotation of one drive shaft may overrun more than an angle required to actuate to the respective positions and this involves the risk of electric shortage or ground fault.
The three-position actuators according to Conventional Examples 1 and 2 are configured such that the elastic force of a spring is used as a supplementary driving source to actuate the disconnecting switch and the earthing switch to the circuit opening position or circuit closing position. Accordingly, noise may be generated due to collision between a movable mechanism using the expansion and contraction of the spring and a stopper mechanism limiting the displacement of the movable mechanism, an unskilled person may have difficulties in actuation because high manual force is required for manual actuation, thus leading to incomplete actuation, and parts may be abraded and damaged due to collision.